Process of obtaining bright and semibright electrodeposits of nickel



PATENT A 2,208,657 OFFICE PROCESS OF OBTAINING BRIGHT AND SEMI- BRIGHT ELECTRODEPOSITS OF NICKEL Q Marcel Ballay, Paris, France, assignor to The International Nickel Company, Inc., New York, r N. Y., a corporation of Delaware Nil-Drawin Application October 26, 1931, Se- -rial No. 171,059. In France November 16, 1

11 Claims. (01. 204-14) The present invention relates to the electro deposition of nickel in bright or semibright form.

Most of the known processes for the. electrodeposition of nickel give deposits which are more or less matte and which require a flnal polishing operation in order to give them the desired brilliant appearance. Processes for the direct deposition of bright nickel are known, the-electrolyte generally consisting of a solution of nickel salts containing an organic colloid. The deposits obtained by such prior processes are very brittle and consequently the thickness of the deposit is always limited to very low values. This disadvantage is partly attributable to the unsatisfactory nature of the colloids which have been used.

One of the principal difllculties was due to the coagulation of the colloid which occurred more or less slowly during the operation of the bath. The colloid would fiocculate and adhere to the surfaces of the pieces being plated whereby highly unsatisfactory platings were produced. The proportion of some colloids had to be maintained within critical limits from which; even slight departure resulted in the production of practically worthless deposits. The stability was frequently strongly influenced by variations in the pH value.

Moreover it was not in general possible to obtain a good deposit directly on steel, and an initial coating with copper to form an undercoating was found necessary to obtain a bright protective layer of nickel.

I have discovered a. new process of obtaining 36 bright and semibright deposits of nickel which is efllcient and economical and which avoids the defects set forth hereinabove to a large extent by using an electrolyte comprising a soluble salt of nickel together with a colloid of egg or blood 40 albumen and by operating the bath containing the electrolyte at a high pH value.

It is an object of the present invention to provide an improved process of obtaining bright and semibright deposits of nickel which may be of substantial depth and which are relatively free from brittleness and cracks.

It is another object of the present invention to provide a process for the electrodeposition of nickel which can be readily regulated to produce bright or semibright deposits 01' nickel.

It is a further object of the invention to provide an electroplating bath containing a nickel salt and a stable colloid.

The invention .also contemplates an improved method of adding a colloid to an electroplating bath containing a nickel salt whereby the proper colloid concentration can be maintained to-produce brightand semibright nickel deposits.

It is also within the contemplation of the invention to. provide a process ior depositing a bright or semibright protective coating of nickel I directly upon a steel body.

' invention.

. Generally speaking, the present invention contemplates a process for the production of bright or semibright deposits of nickel by the use of an electrolyte comprising a soluble salt of nickel together with a colloid in the form of egg albumen or blood albumen, the electrolyte being operated at a pH value not less than about 6.7 and not great enough to cause precipitation of basic nickel salts. Throughout the present speciflca- 15 tion and claims, the pH value referred to is the value obtained by using bromo-thymol-blue as indicator. The pH. value beyond which precipitation of basic nickel salts takes place is in the neighborhood of 7.0 or a little higher and 90 the range about6.9 to about 7.0 constitutes the preferred range in operating the present process. In order to keep the bath at the operative pH value it is convenient to include an ammonium salt in the electrolyte for example, am- :5 monium sulphate. The ammonium salt exercises a buflering action and keeps the pH value within the desired range- It is also desirable that the electrolyte should'contain a chloride, such as sodium chloride or nickel chloride. An alkali metal sulphate or magnesium sulphate may also be added to the bath as these salts are found to enlarge the range in which good deposits are obtained.

Baths having the composition described above 35 yield bright deposits which are relatively non-brittle and the thickness of which may exceed millimeter. The process isparticularly adapted for the production of bright coatings, relatively free from brittleness, having a thick- 40 ness of about 0.020 to about 0.025 millimeter and these may be deposited directly on to steel in order to protect it against corrosion by atmospheric or other corrosive agents. The process, however, is particularly suitable for the production of semibright deposits, that is to say, of deposits which can be polished very rapidly with a disc or other soft abrasive materials to give a bright surface. In this case, it is possible to obtain without difliculty coatings of a thickness m which exceed A; of a millimeter.

The albumen may be introduced into the electrolyte by mixing it with salts constituting the electrolyte during the preparatiomof the latter. The electrolyte is then heated to boiling point and 66 filtered to separate the precipitated albumen. In this case thequantity or albumen added may be varied between about 1 and about 20 centigrams per liter of electrolyte.

An alternative and preferred process, however, 00

is to prepare a concentrated solution of albumen which is added according to the requirements of the nickel plating solution. The preparation of this solution can be carried out in the following manner:--

Albumen is digested when cold with an aqueous solution of a soluble nickel salt, such as nickel sulphate containing, for example, about 50 grams of crystallized salt per liter; after digesting, the solution is raised to boiling point and the major part of the albumen coagulates. The liquid is filtered and the resultant concentrated solution may be added to the electrolyte in the quantity desired. If the concentrated solution of colloid is made, for example, with about 10 grams of albumen per litre and about 50 grams of nickel sulphate per liter, the quantity to be added to the nickel plating electrolyte can be varied according to the results desired between about 1 and about 20 cc. per liter. It has been found that poor results are obtained when the concentrated solution of colloid is made up with pure water, that is to say, in the absence of nickel sulphate. The nickel sulphate may, however, be replaced by other metallic salts and a mixture of nickel sulphate and sodium sulphate for example, gives satisfactory results.

The conditions under which the nickel plating is carried out vary according to the brightness which it is desired that the deposits should possess. The quantity of albumen, temperature, agitation, density of the cathode current all affeet the brightness of the deposit. At any particular temperature and current density, the brightness increases with the albumen concentration. With low current density and in the presence of a substantial amount of albumen, bright deposits are obtained. When the quantity of albumen is kept constant the brightness of the deposit decreases as the current density is raised. The current density can, of course, be increased by increasing the temperature.

Although satisfactory results are obtained at ordinary temperatures with low current density (less than about 1 amp. per sq. dm.) it is preferred to operate the bath at a temperature between about 25 and about 55 C. and at the same time subject it to agitation by passing in a current of air. If the albumen content is large the agitation may produce after some time the formation of a foam which is more or less abundant but this is not disadvantageous because the articles can be introduced transversely to this foam without the appearance of the deposit being impaired.

For the purpose of giving those skilled in the art a better understanding of the invention the following illustrative example of a suitable composition for the electrolyte and examples of operating conditions will be given:

THE Emc'raonwa A suitable composition for the electrolyte is substantially as follows:

Grams per liter NI2SO4.'7H20, about 150 (NH4)2SO4, about 15 NaCl, about l0 NazSO4J0H2O, about l 100 These proportions provide a bath capable of giving satisfactory results but they are described merely by way of example and may be varied within appropriate limits. Moreover, the sodium chloride in the above mixture can be replaced by another chloride, for example, nickel chloride OPERATING CONDITIONS Example No. 1

For the purpose of obtaining a bright deposit the following conditions have given satisfactory results:

Temperature of bathabout 40 to 45 C.

Albumen solution about 10 cc. per liter of bath.

pH about 7.

Current density about 2 amperes per sq-.dm.

Example N0. 2

For the purpose of obtaining a semi-bright deposit the following conditions have given satisfactory results:

Temperature of bathabout 35 to 55 C. Albumen solution about 10 cc. per liter of bath.

pH about 7.

Current density about 2 to 4 amperes per sq. dm.

If the current density is increased to about 5. or 6 amperes per sq. dm., and the temperature maintained at about 50 C., the appearance of the plated object is slightly less satisfactory when removed from the bath, but the deposit may be readily brightened.

The electrolytic bath described above is comparatively cheap, the process and maintenance are easy and it is possible to obtain without an intermediate underlayer bright deposits on steel which offer good protection against corrosion and semibright coatings easy to polish and of a thickness which can attain and even exceed A millimeter.

I claim:

l. A process for electroplating objects with a plating of bright or semibright nickel which comprises preparing an electrolyte containing nickel sulfate and about 1 to about 20 centigrams of albumenoid material per liter of said electrolyte, said albumenoid material being selected from the group consisting of egg albumen and blood albumen and being substantially devoid of albumenoid material coagulable at a boiling tem-- perature in a 5% aqueous solution of nickel sulfate, immersing the object to be plated in said electrolyte, and electrodepositing thereon a plating of nickel. I

2. A process for electroplating objects with a plating of bright or semibright nickel, which comprises preparing an electrolytic bath containing nickel sulfate, an alkali metal chloride, at least one sulfate selected from the group consisting of ammonium sulfate, alkali metal sulfates and magnesium sulfate, and about 1 cc. to about 20 cc. per liter of an aqueous solution of albumen selected from the group consisting of egg albumen and blood albumen and being stabilized to nickel sulfate, said albumen solution having been prepared by digesting said albumen with an aqueous solution of nickel sulfate by coagulating at least a portion of said selected albumen by raising the temperature of said aqueous solution to about 9,908,657 the boiling point and by separating said coagulated albumen from said solution whereby a solution of albumen stabilized to nickel sulfate is obtained; and operating said bath at a pH of about meter and being relatively free from brittleness.

3. A process for electroplating objects with a plating of bright or semibright nickel which comprises preparing an electrolytic bath containing nickel sulfate, at least one chloride selected from the group consisting of nickel chloride and alkali metal chlorides, at least one sulfate selected from the group consisting of ammonium sulfate, alkali metal sulfate and magnesium sulfate, and about 1 cc. to about 20 cc. per liter of bath of a solution of albumen stabilized to nickel sulfate, said albumen being selected from the group consisting of egg albumen and blood albumen and having been prepared by digesting said albumen with an aqueous solution of nickel sulfate, by coagulating at least a portion of said albumen by heating and by separating said coagulated albumen from said solution whereby a solution of albumen stabilized to nickel sulfate'is obtained; immersing an object to be plated in said electrolytic bath as cathode; and operating said bath at a pH of about 6.7 to about 7.0 while maintaining the temperature of said bath between about 25 C. and about C. to plate said object with a bright nickel plating having a thickness of about 0.02 millimeter and being relatively free from brittleness.

4. A process for electroplating objects with a plating of bright or semibright nickel, which comprises preparing a nickel plating electrolyte containing nickel sulfate together with about 1 to about 20 centigrams of albumenoid material per liter of said electrolyte, said albumenoid material being selected from the group consisting of egg albumen and blood albumen, and having been prepared by digesting said albumenoid material in said electrolyte, by coagulating at least a portion of said albumenoid material by heating said electrolyte to about the boiling point thereof and by removing said coagulated albumen from said electrolyte whereby an electrolyte containing albumen stabilized to nickel sulfate is obtained; operating the electrolyte at a pH value of about 6.7 to about 7.0; maintaining the temperature of the electrolyte between about 25 C. and about 55 0.; and plating an object at a current density of about 2 to about 6 amperes per square decimeter in the aforesaid electrolyte.

5. A process for preparing an addition solution for a nickel electroplating bath for the electrode-- position of bright or semibright nickel, which comprises preparing an aqueous solution containing about 50 grams of nickel sulfate per liter, adding about 10 grams per liter of albumenoid material selected from the group consisting of egg albumen and blood albumen, digesting said albumenoid material in said solution in the cold to obtain digested albumenoid material, said digested albumenoid material being not precipitated and not coagulated in the presence of nickel sulfate, heating the solution containing said digested albumenoid material to the boiling point to coagulate coa'guiable albumenoid material and separating said coagulated material from said solution whereby a solution is obtained containing albumenoid material practically completely soluble in nickel sulfate and substantially devoid of albumenoid material precipltable in nickel sulfate electroplating baths.

6. A process for preparing electrolyte for the electrodeposition of bright and semibright nickel plating which comprises preparing an aqueous solution containingnickel sulfate, ammonium sulfate, a chloride selected from the group consisting of nickel chloride and sodium chloride, and a sulfate selected from the group consisting of alkali metal sulfates and magnesium sulfates, adding to said aqueous solution about 1 to about 20 centlgrams per liter '1 albumenoid material selected from the group consisting of egg albumen and blood albumen,digesting said albumenoid material to obtain albumenoid material not coagulated and not precipitated at the boiling point of said aqueous solution, heating said aqueous solution to the boiling point thereof to precipitate and coagulate a portion of said albumenoid material, and separating said precipitated'and coagulated albumenoid material from said aqueous solution wherebyan aqueous solution containing digested albumenoid material practically completely soluble in the presence of nickel sulfate and substantially devoid of albumenoid material precipitable and coagulable in the presence of nickel sulfate is obtained.

7. An electroplating'bath for the electrodeposition of bright and semibright nickel containing nickel sulfate and about one to about twenty centigrams of albumenoid material per liter of bath,

. said albumenoid material being selected'from the group consisting of egg albumen and blood albumen and said albumenoid material being not coagulated at the boiling temperature in a 5% aqueous solution of nickel sulfate.

8. A plating bath foruse in the electrodeposition of bright and semibright nickel platings, comprising an aqueous solution containing a soluble salt of nickel selected from the group consisting of nickel sulfate and nickel chloride, and about 1 to about 20 centigrams per liter of said solution of animal albumenoid material selected from the group consisting of egg albumen and blood albumen, and havingbeen prepared by di-- gesting the selected albumenoid material in said aqueous solution to obtain digested albumenoid material and coagulable albumenoid material, by coagulating said coagulable albumenoid material by raising the temperature of said aqueous solution to about the boiling point thereof, and by separating coagulated albumenoid material from said aqueous solution.

9. A plating bath for use in the electrodeposition of bright and semibright nickel plating, comprising a solution of nickel sulfate, ammonium I sulfate, and alkali metal chloride in a concentration suitable for electrodepositing nickel and about one to about 20 centigrams per liter of. said solution of plating-bath-stable animal albumenoid material selected from the group consisting of egg albumen and blood albumen, said albumenoid material having been prepared by digesting albumenoid material in a solution containing nickel sulfate to obtain coagulable albumenoid material and digested albumenoid material, by coagulating said coagulable albumenoid material by raising the temperature of said solution containing nickel sulfate, and by separating coagulated albumenoid material whereby a solution containing albumenoid material not precipitable and not coagulable by 5% nickel sulfate is obtained.

tion of bright and semibright nickel platlngs, comprising a solution of nickel sulfate, ammonium sulfate, an alkali metal chloride, 9. sulfate selected from the group consisting of an alkali metal sulfate and magnesium sulfate in concentration suitable for the electrodeposition of nickel and about 1 to about 20 centigrams of albumenoid material per liter of said bath, said albumenoid material being selected from the group consisting of egg albumen and blood albumen. and having been prepared by digesting said selected albumenoid material in said bath to obtain coagulable albumenoid material and digested albumenoid material, by coagulating said coagulable albumenoid material by raising the temperature of said bath and by separating said coagulated albumenoid material from said bath whereby a bath containing digested albumenoid is obtained.

11. A plating bath for use in the electrodeposition of bright and semibright nickel plating, comprising an aqueous solution containing the following ingredients per liter:

about 150 grams of nickel sulfate about 15 grams of ammonium sulfate about 10 grams of sodium chloride about 100 grams of sodium sulfate about 1 to about 20 cc. of a solution of stabilized egg albumen, 

